Intermolecular Forces

What is the structure for an ionic bond?

Crystal lattice

What are the structures for covalent bonds?

Individual molecules and networks

What is the structure for metallic bonds?

A sea of electrons

What strength does an ionic bond have?

Strong electrostatic forces (ionic)

What is the strength of molecular covalent bonds?

Weak intermolecular forces

What is the strength of network covalent bonds

Strong covalent bonds

What is the strength of a metallic bond?

Strong electrostatic forces (metallic)

What are the properties of an ionic crystal lattice?

Brittle, High MP (melting point), usually soluble in water

What are the properties of a covalent molecule?

Soft solids, low MP, sometimes soluble in water

What are the properties of covalent networks?

Very hard, extremely high MP, NOT soluble in water

What are the properties of metallic electron seas?

Malleable, MP varies, NOT soluble in water

Why do substances have different physical properties

The bond type determines the structure, the structure determines the strength of forces, and the strength of forces affect the properties.

Why do strong attractive forces yield high melting and boiling points?

The particles are held tightly and require more energy/heat to separate them.

Ionic melting point?

Strong electrostatic forces → high MP

Molecular covalent melting point?

weak intermolecular forces → low MP

Network covalent melting point

Covalent bonds → extremely high MP

Metallix melting point?

Strong electrostatic forces → varies

What are inTRAmolecular forces?

Forces within molecules. Ex: Covalent, ionic, and metallic bonds

What are inTERmolecular forces?

Forces between different molecules. Ex: hydrogen bonding, dipole-dipole interactions, and London dispersion forces (LDFs)

Order the intermolecular forces from weakest to strongest

Dispersion forces < dipole-dipole interactions < hydrogen bonds

Who does dipole-dipole interactions?

Polar molecules

What are dipole-dipole interactions?

Attraction between the partially positive side of end molecule and the partially negative side of another.

What are dipoles?

The positive or negative side of a molecule. They are created by unevenly shared electrons

Who does hydrogen bonds?

H+ FON (hydrogen bonded with Flourine, Oxygen, or Nitrogen)

What are hydrogen bonds?

A stronger dipole-dipole interaction when H is covalently bonded to a very electronegative atom (FON). A strong dipole is formed.

Who does LDFs?

All covalent molecules

What are LDFs?

Momentary electron imbalance creates instantaneous dipole moments, even in neutral and nonpolar molecules. Larger molecules hace more electrons, become more “sloshy” and are stronger.

How do you determine IMFs (intermolecular forces) in a substance?

All molecules have LDFs.

Determine if the molecules is polar. If so, there are dipole-dipole interactions.

Check for H-bonds with FON. If so, there’s a hydrogen bond

What affects the strength of an ionic bond?

Ion charge: greater charge= greater electrostatic attraction (greater effect than size)

Ion radius: smaller ions= greater the electrostatic attraction

Greater electrostatic attraction→stronger bond→higher MP, BP